\documentclass[oldfontcommands]{memoir}
\usepackage{graphicx}
\usepackage{hyperref}
%\usepackage{authordate1-4}

\semiisopage[12]
\checkandfixthelayout

\newcommand{\gl}{gsas\_language}

\begin{document}

\include{frontmatter}

\include{introduction}

\include{installation}

\include{examples}

\include{commands}

\backmatter

%\bibliographystyle{authordate2}
\bibliographystyle{plain}
\bibliography{gsaslanguage_man}

\end{document}